All cells are covered with a dense and complex array of sugar chains. Sialic acids (Sias) are a family of nine-carbon sugars that are typically present at the outermost units of these sugar chains. By virtue of their terminal position, sialic acids act as binding sites for many exogenous and endogenous receptors such as the Influenza viruses and the Siglec family of endogenous proteins. Such sugars are thus useful drug targets for the prevention and treatment of infection. They are also involved in various biological and pathological processes such as neuronal plasticity and cancer metastasis. In many of these instances, the precise structures of the sialic acid and the residues it is attached to play critical roles. Thus, studying sialic acid functions is of great biological importance. In addition, many sialic acids are obtained through certain dietary sources (red meat and diary products), and may also be associated with certain disease states, such as cancer and heart disease.